Mesa type semiconductor device and manufacturing method thereof
View Patent ↗Problems with a conventional mesa type semiconductor device, which are deterioration in a withstand voltage and occurrence of a leakage current caused by reduced thickness of an insulation film on an inner wall of a mesa groove corresponding to a PN junction, are solved using an inexpensive material, and a mesa type semiconductor device of high withstand voltage and high reliability is offered together with its manufacturing method. A stable protection film made of a thermal oxide film is formed on the inner wall of the mesa groove in the mesa type semiconductor device to cover and protect the PN junction, and an insulation film having negative electric charges is formed to fill a space in the mesa groove covered with the thermal oxide film so that an electron accumulation layer is not easily formed at an interface between an N − type semiconductor layer and the thermal oxide film. With the structure described above, an influence of the positive electric charges in the thermal oxide film is weakened and an extension of a depletion layer into the N − type semiconductor layer at the interface with the thermal oxide film is secured.
1. A mesa type semiconductor device comprising:
a semiconductor substrate of a first general conductivity type;
a first semiconductor layer of the first general conductivity type disposed on the semiconductor substrate, an impurity concentration of the first semiconductor layer being lower than an impurity concentration of the semiconductor substrate;
a second semiconductor layer of a second general conductivity type disposed on the first semiconductor layer so as to form a PN junction between the first and second semiconductor layers;
a mesa groove penetrating into the semiconductor substrate through the first and second semiconductor layers;
an oxide film disposed on the second semiconductor layer and in the mesa groove;
an organic insulation film disposed in the mesa groove so as to cover the oxide film at the PN junction and only a portion of the top surface of the second semiconductor layer, the portion being adjacent to and contiguous with the groove, the organic insulation film being in contact with the oxide film at the covered portion of the top surface of the second semiconductor layer; and
a wiring disposed on the oxide film.
2. The semiconductor device of claim 1 , wherein the organic insulation film comprises an organic resist or an epoxy resin.
3. The semiconductor device of claim 1 , further comprising a passivation film disposed on the organic insulation film so as to be in contact with the oxide film.
4. The semiconductor device of claim 3 , wherein a width of the passivation film is larger than a width of the mesa groove.
5. A mesa type semiconductor device comprising:
a semiconductor substrate of a first general conductivity type;
a first semiconductor layer of the first general conductivity type disposed on the semiconductor substrate, an impurity concentration of the first semiconductor layer being lower than an impurity concentration of the semiconductor substrate;
a second semiconductor layer of a second general conductivity type disposed on the first semiconductor layer so as to form a PN junction between the first and second semiconductor layers;
a mesa groove penetrating into the semiconductor substrate through the first and second semiconductor layers;
an oxide film disposed in the mesa groove so as to fill the mesa groove substantially completely and to cover only a portion of a top surface of the second semiconductor layer;
an organic insulation film disposed on the oxide film; and
a wiring disposed on the oxide film.
6. The semiconductor device of claim 5 , wherein the organic insulation film comprises an organic resist or an epoxy resin.
7. The mesa type semiconductor device of claim 5 , wherein a width of the mesa groove is 5 μm or smaller.
8. A method of manufacturing a mesa type semiconductor device, comprising:
providing a semiconductor substrate of a first general conductivity type;
forming a first semiconductor layer of the first general conductivity type on the semiconductor substrate, an impurity concentration of the first semiconductor layer being lower than an impurity concentration of the semiconductor substrate;
forming a second semiconductor layer of a second general conductivity type on the first semiconductor layer;
forming a mask on the second semiconductor layer;
etching the second semiconductor layer, the first semiconductor layer and the semiconductor substrate using the mask so as to form a groove so that the semiconductor substrate is exposed at a bottom of the groove;
forming an oxide film in the groove and on a top surface of the second semiconductor layer; and
forming an organic insulation film in the groove so as to cover the oxide film and only a portion of the top surface of the second semiconductor layer, the portion being adjacent to and contiguous with the groove, the organic insulation film being formed so as to have a dent at and above the groove.
9. The method of claim 1 , wherein the organic insulation film comprises an organic resist or an epoxy resin.
10. A method of manufacturing a mesa type semiconductor device, comprising:
providing a semiconductor substrate of a first general conductivity type;
forming a first semiconductor layer of the first general conductivity type on the semiconductor substrate, an impurity concentration of the first semiconductor layer being lower than an impurity concentration of the semiconductor substrate;
forming a second semiconductor layer of a second general conductivity type on the first semiconductor layer;
forming a mask on the second semiconductor layer;
etching the second semiconductor layer, the first semiconductor layer and the semiconductor substrate using the mask so as to form a groove so that the semiconductor substrate is exposed at a bottom of the groove; and
forming an oxide film so as to fill the groove substantially completely and to cover only a portion of a top surface of the second semiconductor layer.
11. The method of claim 10 , further comprising forming an organic insulation film on the oxide film.
12. The method of claim 11 , wherein the organic insulation film comprises an organic resist or an epoxy resin.